In addition to melee reactions, other non-vanilla behaviour I've noticed is that terror units with arcing weapons will reaction fire even though traditionally they could not react. Aliens carrying blaster launchers/DPL launchers will also fire at point blank range, so you can no longer rely on their sense of self preservation as a last ditch effort to saving yourself.
I'm guessing these were a deliberate design choice. However I do feel these need to be toggle-able in the options like many of the other introduced features.
